DAC Info that may be helpful

Discussion in 'Hi-Fi Stereo Systems & Separates' started by CJROSS, Jul 18, 2002.

  1. CJROSS

    CJROSS
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    DAC Info

    This is a post to newer members on the forum who have a DVD player and wish to get better sounds from their CD playback and the option of adding a DAC to their system gives, rather than buying another CDP . This was wrote for another hifi forum but is equally at home here with all the DVD-V owners looking for a stereo sound upgrade. Apologies to all the dudes who know what DACs are but you’d be surprised how many people don’t know about them and just blindly purchase CDPs.

    What is a DAC : A DAC is a digital to analogue convertor that is generally found inside Integrated (One Box) CDPs that convert the digital signal from a CDs laser pickup to an electric analogue signal for your amplifier. Here is a better run down http://www.howstuffworks.com/cd2.htm but DACs are available in their own right as well as Int. CDPs. All you need is a CD or DVD transport to feed your DAC a signal. So in effect a DAC+Tranport is a 2 box CDP.

    What is a Transport : A Transport is a digital source with a digital output that can be used to feed an offboard DAC, they need to have a digital output of some sort to qualify as a transport, be it Optical Toslink, Coaxial SDif 75 ohms RCA/BNC plugged connectors or Balanced AES/XLR 110 ohms connectors. These are generally dedicated CD transports (with no analogue outputs), Int. CD players, DVD-V/A & SACD players which all are capable of playing rebdook CDs as well. Note that MD, DAT, DAB have digital outputs that send a sampling rate of 44.1 khz pcm signal like the redbook CD standard as well. These can be sent to another DAC for processing rather than listening to the units onboard (generally lesser quality) DAC.

    How do I hook up a DAC : Simply look at the back of your current CDP - DVD, see what type of digital output is has, then make sure the DAC your thinking of has the same connector, the most common on CDP/DVD is the RCA 75ohm Coaxial connector, then hook a 75ohm digital cable from Transport to DAC. Then like your current CDP use a set of normal ICs to take the analogue signal from DAC to Amp.

    What type of connections are best : The generally accepted view is that AES/XLR Balanced connection which send a 110ohm signal are the best, this type of signal is generally used in long run applications like studios, the actual benefit in home hifi is debatable. Next up is the most common : the 75 ohm Coaxial connection this comes in 2 plug types, BNC (which is the better less jittery) & the more common RCA plug (like normal ICs) this is because the RCA is not a true 75 ohm connection. Finally the Optical Toslink connection is usually regarded as the lowest quality. Although saying that, many people find Toslink pretty good.

    What is Jitter : http://www.digido.com/jitteressay.html or http://www.jitter.de/english/engc_navfr.html these are good places to start, but in general terms Jitter is time-base error. It is caused by varying time delays in the circuit paths from component to component in the signal path. Jitter is the main problem in CD transports to offboard DACs, Jitter is a cause of glare, harshness, lack of soundstage and loss of low level detail apparent in most CD replay systems.

    How can we deal with Jitter : The 2 most common ways of dealing with Jitter are : at the CD transport, where reclocking (re-timing) the data prior to output can supress jitter, check out these mods available : http://www.trichordresearch.com/cd_player_upgrades.html Or you can choose a DAC that is not as effected by jitter as others. These are generally true recovery clocking DACs which suppress jitter, by using PLLs (Phase Locked Loops) in simple terms the more PLLs a DAC uses in recovery the better it is at handling jittery input signal (and therefore is not too transport dependant). RAM buffer technology devices which effectively elminate jitter are interesting new devices which are now appearing on the market http://195.40.133.90/website/products/dac64.htm

    Can I make my own DAC : Yup duders http://www.tnt-audio.com/clinica/solidstate.html

    At what point should I use a DAC : IMHO once you go to upgrade your current Int. CDP going on to another Int. CDP means that all you are doing is paying for transport costs again your not actually getting "Sound Per Pound" Thats where the offboard DAC comes in. I think that most £300 CDP or DVD players with the addition of a DAC can really transform the CD playback of the existing transport into £1000+ territory. There are other benefits, if your transport packs in your not paying for the DAC section again when you buy another CDP. When your transport goes then adding a similar priced CDP/DVD will do the job. This Costs less in the long run. Most DACs have multiple inputs so hooking up digital sources like MD, CDR, DAB actually costs less money for expensive ICs, you cut down the need for loads of inputs on amps (ie you only need the DAC input for digital sources) further processing from digital sources to a well designed DAC will have positive effect on your other digital sources performance. Owners of existing DVD-V players should not be buying another integrated CDP until they check out DAC you will get more perfromance for your money.

    Whats the bad news : Well it is a 2 box solution, you will need another plug, another shelf, a digital cable and an understanding SWMBO for the DAC addiction that comes once you own one.

    Future DAC Dudes here are some links to DACs on the net that may come in handy in your search for info on specific DACs you may be interested in.

    http://www.ecoustics.com/Home/Home_Audio/DAC_and_Transports/DAC_and_Transport_Reviews/
    http://www.audioasylum.com/audio/digital/bbs.html
    http://www.stereophile.com/showcategory.cgi?category=Digital Source Reviews

    Final disclaimer : Int. CDPs sound wonderful TOO !! But DACs are better IMHO !!

    Enjoy dudes !!
     
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  2. Nic Rhodes

    Nic Rhodes
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    Thanks for your effort here. I think we can use this as the FAQ on DACs now. It cover everything for a newbie. Well done.
     
  3. ReTrO

    ReTrO
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    If anyone is considering getting a out-board DAC for their cheap CD, or DVD player then seriously consider the Cambridge Audio DAC Magic II. It's a Richer Sounds product, very well received, and certainly sounds good as a budget addon. I think it is either £99 or £149, will do both optical and coax in and will decode upto 48khz digtal streams, aswell as doing HDCD.

    It also acts as an isolation table for the player, as it comes with a set of CA branded neoprene 'squash' balls.:)
     
  4. Electric Mayhem

    Electric Mayhem
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    Very useful info. I´ve stuck the thread so it will be easier to find/see.

    Nice one.
     
  5. CJROSS

    CJROSS
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    Yep Retro that is a little beauty - Ive have heard good reports of it on other boards, Im sure it is £99 - a sure fire no brainer for someone with a £200 DVD-V player wanting better performance and it saves shelf space slotting in underneath your DVD whilst isolating it. And IMHO a little DAC like this takes your DVD player into the £300 CDP area. In fact it does everything that the TAG DAC 20 does even down to the isolation feet. Well Im not sure about the reclocking & extra PLLs but a good addition to a DVD-V player non-the less.

    Cheers Jase !! I hope more dudes with DVD-Vs add DACs it is such a wonderful moment when you slot a good quality DAC into your system for the same price as a mid level CDP and a little voice in your head says :

    "This will do very nicely indeed"

    Later dudes !!
     
  6. tvr

    tvr
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    Having read earlier comments,I am quite interested in the TAG DAC 20.
    Can owners let me know where and how much to pay for one.??
    Thanks in advance

    TVR
     
  7. Nic Rhodes

    Nic Rhodes
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    £450 on Tag web site direct from them. I think they used to be £1200.
     
  8. lynx

    lynx
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    Can you elaborate please. Not being picky, just plain thick :)
     
  9. Nic Rhodes

    Nic Rhodes
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    Don't want to jump on CJ toes but I have answered this one already today!

    RCA was NEVER designed as a 75 ohm connector (way back in 1938 I think). It is typically a characteristic impedance of 20-55 ohms. Canare crimp RCAs are 75 ohm however, Tag solder RCAs are pretty decent as well but expensive. BNCs are a TRUE 75 Ohm connector (in their 75 ohm version, avoid the 50 ohm version obviously). Basically RCAs were never made to carry video or digital signals hence they do it badly! :)
     
  10. Electric Mayhem

    Electric Mayhem
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  11. CJROSS

    CJROSS
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    Guys I thought this would come in handy for folks thinking about using a DAC and hooking it up to an existing AV set up. How to connect up a DAC for to a DVD-V Transport which is connected to a DD/DTS 5.1 AV amp for better playback of CD : From the DVD player (Im assuming a DVD-V player with 2 digtal outputs - 1 Coaxial & 1 Optical) the outputs should be routed as follows :

    The Coaxial Output goes to the DAC (This will send a PCM output for CD playback)
    The Optical (Toslink is the Interface Connection type ie little square connector) to the 3802 (This will stream Bitstream DD/DTS for AV playback)

    These 2 digital connections are all you require to do, the type of connection Ie RCA Coaxial is generally felt to be superior to Toslink Optical for streaming PCM and conversely Bitstream is likely to be effected by cable type. So where possible PCM in coaxial. For listening to CD you simply run a set of IC from the DAC to the CD line input (thereby bypassing the AV Amp DACs) the main thing we are trying to do with the DAC is to bypass an AV Amps onboard DACs so we can listen to the stereo DACs processing rather than the AV amps DACs.

    As for the output modes above ie PCM or Bitstream your DVD-V player may autodetect what type of discs your using and set the output that way, if you have an older player or one that does not do this you will have to swtich the mode manually to get the best performance from each format (CD or DVD) check your players manual. The simplest way to think of the signal types is that the DACis a stereo 2 Channel PCM signal and DVD-V is MC 5.1 Bitstream

    One note of caution be sure to never send a DTS signal from a DVD-V through your DAC – a PCM DAC handling a DTS signal sends a very high frequency signal towards the Amp that will generally fry the tweeters on your speakers. One way to safe gurad against this is to switch off the DAC when your watching DTS DVD-Vs, a simple and safe way of protecting your speakers IMO. But you would have to be quite daft to be watching a DTS DVD-V then switch to the CD Line input on the AV Amp with the DAC switched on in the first place, so switch it off when not listening to CDs.

    HTHs
     
  12. deff

    deff
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    ReTro and CJROSS,

    I been to richersound and found the Cambridge Audio S700 (Digital to Analogue converter).

    Is this the same as the Cambridge Audio DAC Magic II.

    I have the pioneer 545 DVD player and a seperate sub £200 Sony CDP I have had for a while.

    I need an upgrade but cannot afford for sometime to due to baby and house DIY so was hoping that the Cambridge Audio DAC Magic II might just do the trick

    Which will benefit my old cdp or the 545?
     
  13. CJROSS

    CJROSS
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  14. ReTrO

    ReTrO
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    If it has mutliple inputs you should be able to use it with both your DVD and CD. Provided you have different digital output options on them.
     
  15. dts_boy

    dts_boy
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    i have just bought the tag dac20 and am VERY happy with it!
    1 question - i have co-ax out of the dvd into the dac and then analogue out into cd line input on my amp. the dd/dts is passed throught the dac via the digital out on the dac and seems to work fine on dd films, it plays nothing through the cd input. haven't tried with dts films yet, will it work the same, will t damage my speakers or should i just use the optical out of my dvd - amp and stop trying to cut corners (and not have to buy another lead:mad: )?
     
  16. ReTrO

    ReTrO
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    For the best sound quality you are best off bypassing the DAC with your DD/DTS optical feed.
     
  17. mick23

    mick23
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    i have nad 540cd player cost £230 (coax only) if i added c/a dac from r/s£99 is this going to improve cd playback, dac has hdcd capability (540 has not) does the amp/av being used have to have (some kind of hdcd decoding ability) i have some hdcd cds this would seem a fairly cheap way of possible (upgrade) rather than purchase a dearer cd player, dac has optical and bnc out , i have only coax is there a way round this, thanks all
     
  18. michaelab

    michaelab
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    Does the TAG DAC 20 have digital pass through? My DVD player (Philips DVDR 890 player/recorder) only has a single coax digital out so if I hooked it up to a DAC I'd want to make sure that the dts/dd signal gets to my AV amp for watching movies. What about other DACs - do most of them have digital pass through?

    On a different note, isn't the problem with DVD players playing CDs that the laser isn't aligned/focussed properly for reading CDs? If that's the case isn't the transport the root of the problem, not the DAC (notwithstanding that the DAC in a DVD player is probably nothing like as good as a separate DAC)?

    If I could slot a TAG DAC 20 into my system and then use my DVD player for good quality CD playback then I could take my CD player (Marantz CD50SE) out and use it somewhere else. I had been thinking about getting a separate CD player.

    Michael.
     
  19. ReTrO

    ReTrO
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    To a certain extent your right about the transports. The onlt problem now is that there are very few CD only transports left that are good, like the one in the Arcam CD72T. A lot of CD players supposedly use DVD mechs though.

    If you can't get a good start then what chance do the DAC's have.
     
  20. Nic Rhodes

    Nic Rhodes
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    The transport is supremely important here. Many are okay into great DACs but when you hear a great transport you then really know what is what. Unfortunately the greatest limiting step is the SPDIF that everyone uses between the two. Jitter and that.....and this is what holds back many Transport / DAC combinations and is probably the reason why many have gone the integrated route.

    Some DACs do have a digital pass through, mainly to help MD players etc.

    You can get some switching SPDIF boxes that might help with more than one connection.
     
  21. CJROSS

    CJROSS
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    Retro – Beekeeper

    Jeez dudes a real hifi thread, marvellous !! I share a lot of your views dudes about transport quality and I know that at the higfher end of the spectrum when using a DAC that can be run off a transport with superior connections such as the DAC 20s ie its 110 XLR input then that is the way to go, but I think in the middle regions of the hifi world (Ie in sub £1000 CDPs) there are very acceptable transports available that can be fed into good quality DACs like the TAG DAC 20, A DAC that has had great attention paid to recovery clocking and the like (this makes transport less critical IMHO), For example the Pioneer 646A had very low jitter traces in one recent review with a Paul Miller lab report Ive seen, the old Sony QS range of FPM puck CDPs 930 & 940 had very small amounts of jitter, does this make then acceptable as transports ? FWIW the best design Ive seen recently for a design of CDP that has had lots of attention for active jitter supression from the digital output, is the £1000 Creek CD53 :

    http://www.creekaudio.co.uk/products/cd53.asp

    With a new customised ultra low jitter master clock and extra circuitry to reduce jitter from the Digital signal Processor, the CD53 truly sings. A re-clocked, low jitter, transformer coupled, co-axial and optical digital output makes it possible to fully realise the potential of high-end stand alone DAC, provided the correct type of interconnect is used.

    To provide a useful upgrade path, the D to A converter, high quality master clock generator, jitter reduction circuitry and regulated power supplies are sited on a separate printed circuit board that can be removed and replaced by new or emerging technologies in the future.


    I call that good design for an Int. CD player with a view to using it as a transport does the CD72T follow this level of design ? AFAIR the Arcam uses a Sony mechanism and usign a mid priced Sony ES CDP will beat it as a transport, even old models long since replaced.

    FWIW Michael I know a lot of dudes who have added that very DAC to a bewlidering amount of transports and all report improvements in their original playback. I added it my system and it is a truly wonderful unit for example Im pretty happy what it can do off a £500 DVD player BTW, Does your DVDR not have an optical output in addition to your coaxial out ? if so run coaxial to DAC, then optical to AV amp for DTS/DD as Retro has said above. If not the TAG DAC may not be for you as Ive heard a dude mentioning that when used in that configuration ie looping a 48Khz signal from the DAC output, made a much leaner sound (the TAG reclocks the info from the DVD player) from his AV amp, best running 2 cables as suggested ie coax – DAC & optical – AV Amp. BTW I think buying an integrated CDP below £1000 is not up to what you could achieve with adding a £450 DAC.

    Ask yourself this dude, you have a transport already are you willing to buy one again in an integrated CDP, this will curtail your sound per pound upgrade in the DAC department. When you can in effect buy a DAC alone the whol cost of the upgrade going on the DAC alone, for example the DAC 20 cost £1200 when new can adding a sub £1000 CDP outshine it ? not IMHO.
     
  22. michaelab

    michaelab
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    Thanks CJROSS. Unfortunately my DVDR only has a single coax digital out - no optical. Are there any SPDIF splitters out there that I could use to split the signal in two, one for the DAC and one for my AV amp? That's assuming of course that a DTS signal won't damage a DAC20 - opinions?

    I might e-mail TAG to see what they say. If I get a DAC I'll have a dilemma: use it with my DVDR so sticking with just one transport for DVD and CD and then have a spare CD player or use it with the CDP to get probably even better sound?? I already have a spare Arcam Alpha 6+ stereo amp so if I could extract the CDP from my system all I'd need is a pair of speakers for a dedicated stereo music system - but then if I was building a dedicated stereo system I'd probably want the DAC there, or at least a newer and better CDP :(

    I have to say that £450 for the DAC 20 is a most tempting proposition...but as a long standing Formula 1 and Ferrari fan I've long harboured a deep hatred for the McLaren F1 team and anything associated with it which I will have to overcome :devil:

    Michael.
     
  23. dts_boy

    dts_boy
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    lol!
    michaelab, excellent reason for not getting the dac! i too am a BIG ferrari fan and got a lot of greif of my wife when i defected and bought one. its well worth the money though, as many have said, with a decent transport (i was using an arcam dv88) it is quite suprising at how much better it is. BTW i compared it to a £2k cd player which was my alternative and the dv88 with a dac20 sounded better, to me anyway!go on, you can always stick a ferrari badge over it;)
     
  24. CJROSS

    CJROSS
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    Right you Tifosi Ferrari luvvin Muthas put em up1! put em up I say !!

    No problem Michael, FWIW mine is run off a Pioneer 717. DTS I agree about the £2K CDPs BTW, I get quite animated when hear some of the crap (IMHO) that is spouted about sub £400 CDPs being superior to this DAC due to it not being connected to a £1000 pure CD Transport using balanced connections (which I agree does sound top notch, just for me a £600 DVD player does as good a job)

    Anyway not really a big F1 fan, Ive really went off it this year as have many other people, I effectively watch the first 5 minutes to see if anyone has the balls to give schummie a run to the first corner. Generally they dont so its zzzzz time . IMHO of course.

    Anyway you boys wont be in F1 next year ;)
     
  25. michaelab

    michaelab
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    I asked them if the DAC20 would passthrough the DVD bitsream signal (DD 5.1 / DTS) unchanged through its digital out. Here's the response from Mark Walker on the helpdesk (I hope he doesn't mind me reproducing it):

    So YES you CAN use the DAC20 in the manner I was hoping....

    Oh God if I order one now my wife will kill me :devil:

    I need a "cooling off period"... :)

    Michael.
     
  26. CJROSS

    CJROSS
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    Hey Michael great news dude, beware though that when you send a pure DTS signal through your DAC 20 to the AV processor, that the CD line input on the Amp is not switched on : I would not imagine that you would do this, ie it would be set to DVD for enjoying 5.1 surround, but in the event of this happening there is a chance of frying your tweeters on your speakers due to the resultant noise that DTS produces when fed via a PCM DAC, ie the DAC 20 trying to send the signal to its onboard DAC for conversion. It is something to be aware of though when running a PCM DAC in an output mode like above. I for eample don’t have this problem as I have my DTS output switched off (I don’t have an AV amp for processing DTS anyway).

    All that needs to be highlighted is that when watching DTS encoded material that you take care to always use the 5.1 surround DACs on the AV amp, ie selecting DVD for playback. And not the CD line input as this will feed the DAC 20 PCM DACs attempt at sending the PCM signal.

    Think of frying eggs on a red hot skillet with the added joys of a high pitched noise that could break glass that is DTS via a PCM DAC : I was lucky I switched off my source after 3 seconds of this happening.

    BTW you dont need a cooling off period, you just nedd to buy er'indoors a pair of Prada or Gucci shoes, trust me on this.
     
  27. michaelab

    michaelab
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    Good point about the DTS signal. Now something else just occured to me which I asked about on the "Amplifiers" forum here but I haven't got a good answer yet (actually someone asked the same question on the HFC forums and he hasn't got a good answer either):

    Do AV Receivers generally convert analog input signals to digital (for DSP, Dolby Pro Logic etc processing) and then back to analog? If this is the case then if I use my AV receiver wouldn't I get the gorgeous DAC20 output mangled again by going through an A/D -> D/A conversion? My AVR (Marantz SR4200) has a feature called "source direct" which disables all DSP etc but I'm not sure that it's a proper "analog bypass".

    I may have to do what ultimately will give me the best sound but leave me with a much more complex system: use my Arcam Alpha 6+ 2ch integrated as a power amp for the front 2 speakers (and send the DAC20 analog output directly to it) and use the pre-outs on my AVR to drive the 2 fronts via the Arcam....

    Michael.
     
  28. Nic Rhodes

    Nic Rhodes
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    Whether a receiver digitises a signal or not is down to the individual receiver. Many now days do on some inputs not on others (normally the 5.1 / 7.1 inputs). This actually brings a great point up. For those who want the purest audiophile signal (from you DAC20) may well be best off feeding this stereo signal via the 5.1 inputs. This way you have no distortion issues with subs of HQ stereo signals and the signal is not digitised, goes straight via a volume control to the power amp section. Feeding a stereo signal via a multi channel input might sound daft but if you want the best sound quality……:)

    Re digitisation of analogue signals. Most receivers do this a 20 bit / 96kHz now days, rarely is this 24 bit. People get very worried by the degredations introduced in this process. The reality is it WORKS really well and most can’t tell any difference. Any differences that are heard are generally not associated with the AD process but ‘other’ processing that is taking place. The reason it works so damn well is there is NO SPDIF to muck everything up. The re-digitisation of analogue signals is well down on my list of worries now I have lived with several systems. Beforehand I was worried like yourself.

    If you want a DSP to be applied to your stereo signal then re-digitisations needs to take place. Most DAC20 users (substitute you favourite) generally want pure stereo though. If you want to apply say PL2 Music I would by pass the DAC20 and feed a digital signal straight to your receiver.
     
  29. CJROSS

    CJROSS
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    Michael Im not sure to be perfectly honest, I have always assumed that just using the analogue line inputs on any amp including the SR4200 is an all analogue effort (why does it does it need to be digitally enhnaced again? Thats extra processing which in a lot of cases degrades the signal), now conversely feeding a digital signal into a SR4200 will force the SR4200s DACs to process the signal even with an analogue bypass in place IMO, simple test just have the digital input selected and switch the bypass on/off see if the sound goes on/off or deterioates.

    Contact Marantz to see what they say as well. There are guys ehre who know how AV recievers work better than me, One being Beekeeper.

    IMHO conencting to the line inputs and listening with anlaogue bypass is the best bet for cD playback, BTW you are indeed correct I think an Arcam 6 will sound superior to the 4200 in hifi terms, again worth a try duder.
     
  30. michaelab

    michaelab
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    Unfortunately my SR4200 doesn't have 5.1 inputs :(

    Just checked the SR4200 specs on the Marantz web site and it DOES do 96kHz/24bit digitisation - so I'm less worried.

    I just ordered by DAC20!!! Unfortunately I won't have a chance to try it out for a couple of weeks as I'm away on business (back in London for 2 weeks). Will post results here eventually.

    Thanks for all the info guys (or should that be dudes? :D )

    Michael.
     

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